Generation of MeV photons and protons in laser picosecond plasmas

Multi-MeV ion production from the interaction of a short laser pulse with a high-density plasma, accompanied by an underdense preplasma, has been studied with a particle-incell simulation and good agreement is found with experiment. The mechanism primarily responsible for the acceleration of ions is identified. Comparison with experiments sheds light on the ion-energy dependence on laser intensity, preplasma scale length, and relative ion energies for a multi-species plasma. Two regimes of maximum ion-energy dependence on laser intensity, I, have been identified: subrelativistic, ∝ I; and relativistic, ∝ √ I . Simulations show that the energy of the accelerated ions versus the preplasma scale length increases linearly and then saturates. In contrast, the ion energy decreases with the thickness of the solid-density plasma.

Review of Scientific Instruments, 2014

High intensity laser-plasma interaction has attracted considerable interest for a number of years. The laser-plasma interaction is accompanied by generation of various charged particle beams, such as high-energy proton and ions with high charge to mass ratio (Q/M; same as multi-charged ions). Results of simultaneous novel measurements of electron-induced photonuclear neutrons (photoneutron), which are a diagnostic of the laser-plasma interaction, are proposed to use for optimization of the laser-plasma ion generation. The proposed method is demonstrated by the laser irradiation with the intensity of 1 × 10 21 W/cm 2 on the metal foil target. The photoneutrons are measured by using NE213 liquid scintillation detectors. Heavy-ion signal is registered with the CR-39 track detector simultaneously. The measured signals of the electron-induced photoneutrons are well reproduced by using the Particle and Heavy Ion Transport code System. The results obtained provide useful approach for analyzing the various laser based ion beams. © 2013 AIP Publishing LLC.

2013

Deutered polyethylene (CD2)n thin and thick targets were irradiated in high vacuum by infrared laser pulses at 1015W/cm2 intensity. The high laser energy transferred to the polymer generates plasma, expanding in vacuum at supersonic velocity, accelerating hydrogen and carbon ions. Deuterium ions at kinetic energies above 4 MeV have been measured by using ion collectors and SiC detectors in time-of-flight configuration. At these energies the deuterium–deuterium collisions may induce over threshold fusion effects, in agreement with the high D-D cross-section valuesaround 3 MeV energy. At the first instants of the plasma generation, during which high temperature, density and ionacceleration occur, the D-D fusions occur as confirmed by the detection of mono-energetic protonsand neutrons with a kinetic energy of 3.0 MeV and 2.5 MeV, respectively, produced by the nuclear reaction. The number of fusion events depends strongly on the experimental set-up, i.e. on the laser parameters (intens...

Plasma Physics Reports, 2004

This paper reviews the many recent advances at the Center for Ultrafast Optical Science (CUOS) at the University of Michigan in multi-MeV ion beam generation from the interaction of short laser pulses focused onto thin foil targets at intensities ranging from 10 17 to 10 19 W/cm 2 . Ion beam characteristics were studied by changing the laser intensity, laser wavelength, target material, and by depositing a well-absorbed coating. We manipulated the proton beam divergence using shaped targets and observed nuclear transformation induced by high-energy protons and deuterons. Qualitative theoretical approaches and fully relativistic two-dimensional particle-in-cell simulations modeled energetic ion generation. Comparison with experiments sheds light on ion energy spectra for multi-species plasma, the dependences of ion-energy on preplasma scale length and solid density plasma thickness, and laser-triggered isotope yield. Theoretical predictions are also made with the aim of studying ion generation for high-power lasers with the energies expected in the near future, and for the relativistic intensity table-top laser, a prototype of which is already in operation at CUOS in the limits of severalcycle pulse duration and a single-wavelength spot size. © 2004 MAIK "Nauk a/ Interperiodica".

Physical Review E, 2009

The paper by Belyaev et al. [Phys. Rev. E 72, 026406 (2005)] reported the first experimental observation of alpha particles produced in the thermonuclear reaction 11 B(p, α) 8 Be induced by laser-irradiation on a 11 B polyethylene (CH2) composite target. The laser used in the experiment is characterized by a picosecond pulse duration and a peak of intensity of 2×10 18 W/cm 2. We suggest that both the background-reduction method adopted in their detection system and the choice of the detection energy region of the reaction products are possibly inadequate. Consequently the total yield reported underestimates the true yield. Based on their observation, we give an estimation of the total yield to be higher than their conclusion, i.e., of the order of 10 5 α per shot.

Eclim 2000: 26th European Conference on Laser Interaction with Matter, 2001

High energy protons with the energy up to 10 MeV were accelerated in the forward direction using a tabletop laser with focusing intensity of 6x 1018W/cm2. When a deuterated polystyrene was deposited on a front surface of a Mylar film and a boron sample was placed behind the laser target we observed the production of 4O atoms of positron active isotope from the reaction "B(d,n)1 'C. The activation results suggest that deuterons were accelerated from the front surface of the laser target.

SPIE Proceedings, 2000

In order to study the ion acceleration in ultra-intense laser plasma interactions, we measured neutron spectra from the D-D ion nuclear reactions in the target. 50-100TW / 0.5-1 ps laser light irradiated obliquely deuterated plastic solid targets with different laser polarizations and intensities. Comparing the neutron spectra with the 3-D Monte-carlo simulation indicates ion acceleration in the rear target normal direction at any polarization and increases in the ion energy with laser intensity.

Physics of Plasmas, 2011

2008

We have compared the acceleration of high-energy ions from the rear surface of thin foils for various prepulse contrast conditions of the ultraintense laser pulse irradiating the targets. The experiments were performed using the Laboratoire pour l'Utilisation des Lasers Intenses 100-TW laser facility with 15-20 J energy pulses of > 10 18 W/cm 2 intensity irradiating aluminum targets of variable thicknesses. The laser pulse contrast ratio ahead of the main pulse (prepulse) was varied using either a fast Pockels cell or a single or double plasma mirror (PM). The latter was installed at an intermediate field position, in between the focusing optics and the target. This way, the effect of reducing the laser prepulse by the PM was optimized. With both methods improving the laser pulse contrast, we have observed that one can significantly reduce the thickness of the target used for proton acceleration and, at the same time, increase 1) the maximum energy of the accelerated protons and 2) the energy conversion efficiency of the process. This offers interesting perspectives from high-energy (5-10 MeV) ion acceleration using sub-petawatt laser facilities. A full characterization of contrast enhancement due to

The Review of Laser Engineering, 2014